1. Field
Embodiments according to the present invention are directed toward a composite positive active material, a positive electrode and a lithium battery containing the composite positive active material, and a method of preparing the composite positive active material.
2. Description of the Related Art
In general, for use as a positive active material for a lithium battery, an oxide of a transition metal compound and lithium is used and examples of such an oxide include LiNiO2, LiCoO2, LiMn2O4, LiFePO4, LiNixCO1-xO2 (0≦x≦1), and LiNi1-x-yCoxMnyO2 (0≦x≦0.5, 0≦y≦0.5). However, such positive active materials have limited electric capacity.
Accordingly, positive electrode materials having various structures have been suggested. For example, according to the demand for high-capacity batteries, a composite-based oxide has been used as an alternative.
For example, from among such composite-based oxides, there is Li2MO3—LiMeO2 (wherein M and Me are transition metal) having a layered structure as an example. The composite-based oxide having a layered structure enables intercalation/deintercalation of a great (e.g., large) amount of Li ions, as compared to other positive active materials, and thus, it has high capacity properties. However, since much lithium is released from Li2MO3, a structural change may occur during charging/discharging cycles and an average voltage decreases due to the translocation of transition metal atoms into empty Li ion sites.
Accordingly, a positive active material with high capacity and improved lifetime properties and high-rate properties is still desired.